Background: Teaching and learning about the history of the profession is consistent with APA's 2023 guidelines for the undergraduate major, a profession-wide competency for graduate students in health service psychology, and important for all students. Objective: The purpose of this article is to present a historical case study with materials for teaching and learning about the historical context, including mental health treatments and patient demographics, during the interwar period at Rockland State Hospital (RSH) in New York. Method: We thematically reviewed and analyzed primary source archival documents, treatment reports, period peer-reviewed journals, related newspaper articles, and publicly available U.S. census data. Results: The theories, diagnostic terminology, and treatments in use at RSH during the interwar period are showcased. This was a pivotal time in the history of psychology. Conclusion: The method and results offer opportunities for teaching and learning about the history of psychology including treatment of marginalized and vulnerable populations. Teaching Implications: Institutionalization in the interwar period offers multiple opportunities for teaching and learning in psychology. The findings can be used in conjunction with discussion questions in the classroom setting. Teaching about the past provides a feedback loop to inform current and future practice.